1. Field of the Invention
The present invention relates to a fuel cell, more particularly relates to a fuel cell in which a cathode layer and anode layer sandwiching a solid electrolyte layer are supplied with a mixed gas of a fuel gas and air mixed together.
2. Description of the Related Art
A cylindrical fuel cell for use as a fuel cell is proposed in Japanese Unexamined Patent Publication (Kokai) No. 7-282823. This cylindrical fuel cell, as shown in FIG. 17, is comprised of a cylindrical base member 100 comprised of a porous ceramic, a porous anode layer (air electrode) 102 formed at the outer circumference of the cylindrical base member 100, a solid electrolyte 104 comprised of yttria-containing stabilized zirconia formed at the outer circumferential surface of the anode layer 102, and a cathode layer (fuel electrode) 106 formed at the outer circumferential surface of the solid electrolyte 104—all formed concentrically. Further, this cylindrical fuel cell has an interconnector 108 passing through the solid electrolyte 104 to be connected with the anode layer 102 and not in contact with the cathode layer 106. The surface of the cell is exposed. In this cylindrical fuel cell, by passing air through the inside the cylindrical base member in an atmosphere of 900 to 1000° C. and passing methane or hydrogen or another fuel gas along the outer circumferential surface of the cathode layer 106, it is possible to generate an electromotive force by the electrochemical reaction between the oxygen in the air and the fuel ingredients in the fuel gas.
Summarizing the problem to be solved by the present invention, according to the cylindrical fuel cell shown in FIG. 17, it is possible to reduce the size compared with a planar fuel cell and possible to easily separate the air flowing through the cylindrical base member 100 and the fuel gas flowing along the outer circumferential surface of the cathode layer 106. However, even with a cylindrical fuel cell, if trying to improve the power generation efficiency by increasing the contact area of the anode layer 102 and cathode layer 106 with the air or fuel gas, the cell has to be made larger in diameter and the fuel cell becomes larger in size.